Thermal quenching of tissue

ABSTRACT

The present invention provides a system for achieving erythema and/or mild edema in an upper layer of skin, without causing blisters, and without the risk of high fluence levels or critical need for cooling.

[0001] This application claims the benefit of U.S. patent applicationSer. No. 09/364,275 filed Jul. 29, 1999 incorporated herein by referencein its entirety.

FIELD OF THE INVENTION

[0002] This invention is related to the delivery of laser or othersource of thermal energy to biological or other tissue for treatmenttherein.

BACKGROUND OF THE INVENTION

[0003] It is sometimes desirable to cause heat affected changes in aselected structure in tissue, such as a vein or hair follicle withoutcausing heat affected changes in tissue adjacent to the selectedstructure. Selective photothermalysis is a method of irradiating with alaser or pulsed light source that is preferentially absorbed by apre-selected target. The amount of energy or fluence delivered to thetarget is chosen such that the temperature rise in the targeted regionresults in an intended thermal treatment of the target.

[0004] Heating of the epidermis may occur during treatment of the targetand several methods have been described for cooling the surface of skinduring and prior to treatment to minimize the risk of thermal injury totissue adjacent to the targeted veins. One early method includedpre-cooling with ice for several minute prior to treatment. U.S. Pat.No. 5,282,797 issued Feb. 1, 1994 to Chess describes a method ofcirculating cooling fluid over a transparent plate in contact with thetreatment area to cool the epidermis during treatment. U.S. Pat. No.5,344,418 issued Sep. 6, 1994 to Ghaffari describes a method whereby acoolant is used for a predetermined time interval in coordination withthe delivery of laser energy to optimize the cooling of the epidermisand minimize cooling of the targeted vessel. U.S. Pat. No. 5,814,040issued Sep. 29, 1998 to Nelson et al. describes a cooling method wherebya cryogenic spurt is applied for a predetermined short time directlyonto the skin in the target region. The time period for cooling isconfined only to the epidermis while leaving the temperature of deeperport wine stains substantially unchanged. Many of the cooling methodsmay limit the amount of significant thermal damage to the epidermisduring treatment.

[0005] It may be desirable to shrink collagen in order to reduce theappearance of undesirable conditions of the skin such as acne scars andwrinkles. The following U.S. patents to Sand teach controlled thermalshrinkage of collagen fibers in the cornea using light at wavelengthsbetween 1.8 and 2.55 microns: U.S. Pat. No. 4,976,709, Class No. 606/5,issued Dec. 11, 1990; U.S. Pat. No. 5,137,530; U.S. Pat. No. 5,304,169;U.S. Pat. No. 5,374,265; and U.S. Pat. 5,484,432.

[0006] U.S. Pat. No. 5,810,801, class no. 606/9 issued Sep. 22, 1998 toAnderson et al. teaches a method and apparatus for treating wrinkles inskin by targeting tissue at a level between 100 microns and 1.2millimeters below the surface, to thermally injure collagen withoutcausing erythema, by using light at wavelengths between 1.3 and 1.8microns. Because of the high scattering and absorption coefficients,precooling is utilized to prevent excess heat build up in the epidermiswhen targeting the region of 100 microns to 1.2 mm below the surface.Specific laser and cooling parameters are selected so as to avoiderythema and achieve improvement in wrinkles as the long term result ofa treatment.

SUMMARY OF THE INVENTION

[0007] The present invention provides a system for achieving erythemaand/or mild edema in an upper layer of skin, without causing blisters,and without the risk of high fluence levels or critical need forcooling.

[0008] The invention uses a source of thermal energy, which may beinfrared in the wavelength range of 1100 nm to 2.9 nm, to causethermally mediated effects in skin. The systems and methods are directedtoward heating the skin with a source of energy which is uniformlyattenuated with depth in skin for a predetermined time period andpredetermined fluence so that the exposure time of the epidermis and thepeak temperature reached by the epidermis are such that the epidermisdoes not blister but the thermally mediated injury in the skin below theepidermis causes a transient erythema to initiate a healing response. Byachieving erythema and/or mild edema in an upper layer of skin, thesystem precludes the risk of high fluence levels or critical need forcooling. The dosage and time period of application are adjusted toprevent excess accumulation of heat in the epidermis, which would causetissue damage. Thermal quenching is used to remove latent heat from thetreatment site to prevent thermal damage to the tissue. Collagenremodeling is induced by distributing the laser energy over a series ofmore benign treatments spaced weeks apart.

[0009] It is therefore an advantage and an object of the presentinvention to provide an improved system for selectively cooling tissueduring photothermal treatment.

[0010] It is a further advantage of the present invention to providesuch a system which uses dynamic cooling to quench heat build up duringand after photothermal treatment.

[0011] It is a further advantage of the present invention to providesuch a system which selectively heats a subsurface structure in tissueand subsequently quenches heat build up in non-target tissue.

[0012] It is a further advantage of the present invention to reduce thelevel of pulsed energy needed for treatment by minimizing precooling ofthe tissue.

[0013] It is a further advantage of the present invention to providesuch a system which selectively heats a subsurface structure in skin tocause thermal affected changes in said subsurface structure withoutsignificant epithelial damage due to subsequent heating from the targetregion.

[0014] It is a further advantage of the present invention to providesuch a system which selectively heats vascular lesions in tissue andquenches subsequent heat build up in epithelial tissue.

[0015] It is a further advantage of the present invention to providesuch a system which selectively heats hair follicles in tissue andquenches subsequent heat build up in epithelial tissue.

[0016] It is a further advantage of the present invention to requireless cooling of the target area than is typically required, resulting inmore efficient heating of the selected target and less thermal damage tosurrounding tissue.

[0017] In a preferred embodiment, the system for generating light energyis a laser system such as but not limited to a solid-state laser,including but not limited to a neodymium-doped yttrium-aluminum-garnet(Nd:YAG) laser.

[0018] In additional preferred embodiments, the system for generatinglight energy is a gas discharge flashlamp or an incandescent-typefilament lamp.

[0019] The energy from the generating system may be directed into orcoupled to a delivery device such as but not limited to a fiber optic orarticulated arm for transmitting the light energy to the target tissue.

[0020] The light energy may be focused on tissue with a focusing lens orsystem of lenses.

[0021] The surface of the tissue may be cooled with a cooling deviceincluding but not limited to an irrigating solution, a spray or flow ofrefrigerant or other cryogenic material, or a transparent window cooledby other active means, or other dynamic or passive cooling means.

[0022] The tissue may be preheated with a heating device such as, butnot limited to an intense light source, a flashlamp, a filament lamp,laser diode, other laser source, electrical current, or otherelectromagnetic or mechanical energy which penetrates into layers oftissue beneath the surface. The preheating can occur simultaneously orjust prior to the surface cooling of tissue from the cooling device suchthat the tissue preheating results in a temperature rise in underlyinglayers of tissue, and a temperature profile results. The pulsedapplication of energy from the energy delivery device results in atemperature profile that preferentially heats a selected structure ortarget in tissue, and the post cooling prevents thermal damage to tissueadjacent to that structure. This also reduces the overall pulse energylevel needed of the pulsed treatment device due to the fact that adesirable temperature profile exists prior to delivery of the pulsedtreatment energy.

[0023] The tissue may be post cooled with a dynamic cooling device suchas, but not limited to a pulse, spray or other flow of refrigerant suchthat the post cooling occurs after a temperature rise in an underlyingtargeted structure and a temperature profile results such that thepulsed application of energy from the energy delivery device results ina temperature profile that preferential heats a selected structure intissue without subsequent undesirable heating to tissue adjacent to thatstructure from thermal conduction.

[0024] Numerous other advantages and features of the present inventionwill become readily apparent from the following detailed description ofthe invention and the embodiments thereof, from the claims and from theaccompanying drawings.

[0025] Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a representative schematic block diagram of a preferredembodiment of a system for thermal quenching of tissue of the presentinvention.

[0027]FIG. 2 is a more detailed representative schematic block diagramof a preferred embodiment of the delivery device shown in FIG. 1 of thepresent invention.

[0028]FIG. 3 is a representative sample data plot of the temperature ofsurface tissue and target tissue achieved by methods and systems of theprior art having precooling.

[0029]FIG. 4 is a representative sample data plot of the temperature ofsurface tissue and target tissue achieved by a preferred embodiment ofthe method and system of the present invention such as shown in FIGS. 1and 2 having precooling.

[0030]FIG. 5 is a representative sample data plot of the temperature ofsurface tissue and target tissue achieved by a preferred embodiment ofthe method and system of the present invention such as shown in FIGS. 1and 2 without precooling.

DETAILED DESCRIPTION

[0031] The description that follows is presented to enable one skilledin the art to make and use the present invention, and is provided in thecontext of a particular application and its requirements. Variousmodifications to the disclosed embodiments will be apparent to thoseskilled in the art, and the general principals discussed below may beapplied to other embodiments and applications without departing from thescope and spirit of the invention. Therefore, the invention is notintended to be limited to the embodiments disclosed, but the inventionis to be given the largest possible scope which is consistent with theprincipals and features described herein.

[0032]FIG. 1 is a representative schematic block diagram of a preferredembodiment of a system 100 for thermal quenching of tissue of thepresent invention. Operation of energy source 102 to produce energy fordelivery by the system 100 is controlled according to control signal 104from control system 106. Control system 106 includes a physicianinterface 108 for operating the system. Said interface 108 optionallyincludes a footswitch for energy delivery, display and interactiveand/or menu driven operation utilizing operator input, prompts, etc.Additional energy delivery control interface means shall be known tothose skilled in the art.

[0033] In a preferred embodiment, energy source 102 is a neodymium dopedyttrium-aluminum-garnet (Nd:YAG) laser, energized by a flash-lamp orlaser diode. Energy source 102 is controlled by control system 106 whichcomprises the software and electronics to monitor and control the lasersystem, and interface 108. The beam of laser energy 110 from the energysource 102 is directed into a delivery device 112 which may be anoptical fiber, a fiber bundle or articulated arm, etc.

[0034] Modern instruments to provide dynamic cooling of the surfacelayers of tissue or other materials are well suited to theseapplications. A coolant spray can be provided through a handpiece or itcould be provided with another separate device. Finally, a connection toa computer and the control system 106 of the energy source 102 willallow the system 100 to utilize electronic or other thermal sensingmeans and obtain feedback control signals for the handpiece. An optimumcooling strategy might be one that uses a post-irradiation cooling spurtthat provides cooling or dissipation of the epidermal heat generated byabsorption of energy in the non-isotropic skin, optionally containingvarious pigmentation levels. An appropriate cryogen spray would beliquid nitrogen or tetrafluoroethane, C₂H₂F₄, an environmentallycompatible, non-toxic, non-flammable freon substitute. In clinicalapplication the distance between the aperture of the spray valve and theskin surface should be maintained at about 20 millimeters.

[0035] In a preferred embodiment of the present invention, upon deliveryof laser energy onto the surface and therethrough, the target tissuewill be raised to the optimal treatment temperature and generally notany higher, in an adequately rapid process, with the surface temperatureof the skin remaining at a temperature below the threshold for damagetemperature. It will be understood that the threshold for damagetemperature is the temperature below which the skin or other tissue canbe elevated without causing temporary or permanent thermal damage, andabove which the tissue may undergo either transient or long termthermally induced physiological change. As described, the wavelength ofirradiated light energy is selectively absorbed by hemoglobin or hairfollicles, or other tissue with pigmentation or chromophores of acertain type, but passes through the surface and overlying/adjacenttissue to the target tissue with minimal absorption. However, once thetarget tissue or structure becomes elevated in temperature, surroundingand adjacent tissue will become hot due to conduction of heat from thetarget tissue or structures. Post-irradiation cooling can then beinitiated, and tissue other than the target tissue is prevented fromincreasing in temperature beyond the threshold of damage or adverseeffect. Adverse effects of elevated tissue surface temperature includediscomfort or pain, thermal denaturing of proteins and necrosis ofindividual cells at the surface only, or deeper tissue ablationpotentially leading to hyperplasia, scarring, or hyperpigmentation, aproliferation of cells formed in response to the induced trauma. In apreferred embodiment of the method of the present invention, heating andsubsequent post-cooling are performed in a predetermined timingsequence, optionally with the use of timer circuits and/or othercontroller means.

[0036] Thus, it will be obvious to those skilled in the art that apassive heat sink includes glass or sapphire tip probes, and other typesof devices to lay on the surface of the skin. It will also be obviousthat a dynamic type of heat sink will refer to those actively cooled byflowing gas or liquid, jets or spurts of coolant such as freon, andother active types of heat exchangers suitable for surface cooling whileirradiating sub-surface portions of collagen tissue. U.S. Pat. No.5,820,626 issued Oct. 13, 1998 to Baumgardner and U.S. application Ser.No. 08/938,923 filed Sep. 26, 1997 by Baumgardner et al., bothincorporated herein by reference in their entireties, teach a coolinglaser handpiece with refillable coolant reservoir, and can be utilizedas a handpiece for delivery device 112 and heat sink 114.

[0037]FIG. 2 is a more detailed representative schematic block diagramof a preferred embodiment of the delivery device 112 shown in FIG. 1 ofthe present invention. The energy from the energy source 102 is directedinto delivery device 112 via a delivery channel 130 which may be a fiberoptic, articulated arm, or an electrical cable etc. At the distal end ofdelivery device 112 is a energy directing means 131 for directing thepulsed energy toward the surface tissue 116 and overlaying tissue 118overlaying the target tissue or structure 120. A nozzle 134 is usefulfor directing coolant from reservoir 135 to the tissue 118, and a valve136 for controlling the coolant interval. A temperature sensor 137 maybe used to monitor the temperature rise of the target tissue 118.Control system 106 monitors the temperature signal from sensor 137 andcontrols valve 136 and energy source 102. Reservoir 135 may be in thedelivery device 112 or elsewhere, and contains a refrigerant which maybe applied to surface tissue 120 by spraying said refrigerant fromcooling nozzle 124 in conjunction with delivery of pulsed treatmentenergy to the patient.

[0038]FIG. 3 is a representative sample data plot of the temperature ofsurface tissue 116 and target tissue 120 achieved by methods and systemsof the prior art having precooling. The waveforms are representative ofoscilloscope-type traces which reproduce signals generated by one ormore thermal detectors. In general, with precooling the coolant isapplied just prior to the delivery to the pulsed energy. Waveform 240indicates the periods of time and associated temperatures of the targettissue and the surface tissue during the processes of the prior art.Initially, as indicated by time period 241, the temperature of thesurface tissue 116 as well as the target tissue 120, as shown in FIGS. 1and 2, are at T_(s) and T_(t) respectively. It will be understood thattypically the skin surface is at a temperature somewhat below actualbody temperature. Typically, this range might be between about 28 andabout 34 degrees Celsius. Furthermore, a target vein, hair follicle orother structure can be assumed to be at about or somewhat just below 37degrees Celsius, or actual body temperature. Once the refrigerant isapplied to surface tissue 116 by opening valve 136 during a subsequenttime period 244, the temperature T_(s) drops to a level determined bythe length of time 244 for which the surface tissue 120 is exposed tothe coolant. By way of example, for time periods of about 30milliseconds, T_(s) may drop from a typical temperature of about 32degrees Celsius to just above 0 degrees Celsius. However, as the targettissues 120 is deeper than the surface 116, initially T_(t) is notsignificantly affected and may drop by only a few degrees. A short delay245 following delivery of refrigerant may be used, and is typicallybetween 0 and 100 milliseconds. This allows time for cooling of at leasta layer of epidermis to a depth of 50 to 250 micrometers. Following timeperiods 244 and optional period 245, the pulsed energy is applied overpredetermined or other time period 246. The time period 246 depends onthe size of the target and the fluence delivered, as indicated byprinciples of selective photothermalysis. For example, in experimentswith an Nd:YAG laser operating at 1064 nanometers, one application of a10 millisecond period and a fluence of 50 joules per square centimeterwas sufficient to treat small blood vessels, and fluences of up to 150joules per square centimeter and time periods of up to 200 millisecondsare useful for treating larger vessels of 1 to 3 millimeters incross-section. During period 246 T_(t) increases to a therapeuticallyeffective value, whereas T_(s) remains below the threshold indicated as250 for patient discomfort or tissue damage.

[0039] Subsequent to treatment, the target tissue 116 cools byconduction of thermal energy to adjacent overlaying tissue 118 includingthe surface tissue 116, with a resultant temperature rise in the targettissue 120 dependant on the size and depth of the target tissue 120. AsT_(t) equalizes with surrounding tissue, the T_(s) may rise above thelevel of patient discomfort and even cause damage to surface tissue 116.

[0040]FIG. 4 is a representative sample data plot of the temperature ofsurface tissue 116 and target tissue 120 achieved by a preferredembodiment of the method and system of the present invention such asshown in FIGS. 1 and 2 having precooling. The method of the presentinvention includes the process of precooling surface tissue 116 andtarget tissue 120 slightly, followed by a short time period 245 andsubsequent delivery of thermal energy to the body during time period 246such as shown in FIG. 3. In the present invention, however, refrigerantis also applied subsequent to the energy pulse by opening valve 136 asdesired or as indicated, thus keeping T_(s) below the threshold fordamage temperature 250. FIG. 4 shows a pulse of coolant applied duringtime period 248 which is subsequent to the application of pulsed energyduring period 246. This results in thermal quenching of the surfacetissue 116. The thermal quenching pulse or other flow of refrigerant orother means for cooling is applied after the beginning of treatmentperiod 246 and may be initiated before or after the end of time period246. It is important that the peak or highest temperature of the surfacetissue 116 never rise above the threshold for damage temperature 250.The time point at which the peak temperature in the surface tissue 116is achieved is dependant on the size and depth of the target 120.

[0041] In one experimental example, cryogenic fluid was applied to thesurface tissue 116 within 10 milliseconds of the end of the energy pulseof time period 246 and for a duration 248 of 20 milliseconds. Forvascular treatment with an Nd:YAG laser with pulse widths of 5milliseconds to 200 milliseconds, the period of thermal quenching 248preferably 10 milliseconds to 30 milliseconds immediately after thetreatment energy. This sequence significantly reduced patient discomfortcompared to treatment with out thermal quenching. The effect of thermalquenching is not dependant on pre-cooling and may be used as the onlymethod of cooling in many cases.

[0042]FIG. 5 is a representative sample data plot of the temperature ofsurface tissue and target tissue achieved by a preferred embodiment ofthe method and system of the present invention such as shown in FIGS. 1and 2 without precooling. As in the method shown in FIG. 4, the thermalquenching pulse or other flow of refrigerant or other means for coolingover time period 248 is applied after the beginning of treatment period246 and may be initiated before or after the end of time period 246. Itis important that the peak or highest temperature of the surface tissue116 never rise above the threshold for damage temperature 250.

[0043] The present invention requires less cooling of the target tissue,structure or area during the treatment phase than is typically required,resulting in more efficient heating of the selected target and lessthermal damage to surrounding tissue.

[0044] It will be understood that while numerous preferred embodimentsof the present invention are presented herein, numerous of theindividual elements and finctional aspects of the embodiments aresimilar. Therefore, it will be understood that structural elements ofthe numerous apparatus disclosed herein having similar or identicalfunction may have like reference numerals associated therewith.

[0045] In a preferred embodiment of the present invention, re-heating oftissue, especially target or subsurface tissue can be useful. U.S.application Ser. No. 09/185,490 filed Nov. 3, 1998 by Koop et al.entitled Subsurface Heating of Tissue teaches methods and systems forperforming subsurface heating of material and tissue, and isincorporated herein by reference in its entirety. With these methods andapparatus, target or subsurface tissue is preheated to an elevated,non-destructive temperature which is somewhat below that of treatment.Thereafter, the temperature of the target tissue or structures is raisedto treatment temperature. Once this second increase in temperature isachieved, the target tissue or structures will conduct heat into thebody, especially to adjacent tissue and surface tissue, at which timethe post-cooling of the present invention can be initiated so as toprevent damage to adjacent tissue or dermis or other surface tissue.

[0046] In one embodiment the invention utilizes an Nd:YAG laser at 1320nm wavelength, (such as the CoolTouch 130, CoolTouch Corp., AuburnCalif.) as the source of treatment energy. At 1320 nm the absorptiondepth in tissue is such that energy is deposited throughout the upperdermis, with most absorption in the epidermis and upper dermis, a regionincluding the top 200 to 400 microns of tissue. The energy falls offapproximately exponentially with the highest level of absorbed energy inthe epidermis. Optical heating of skin follows exposure to the laserenergy. If the time of exposure to the laser is very short compared tothe time required for heat to diffuse out of the area exposed, thethermal relaxation time, than the temperature rise at any depth in theexposed tissue will be proportional to the energy absorbed at thatdepth. However, if the pulse width is comparable or longer to thethermal relaxation time of the exposed tissue than profile oftemperature rise will not be as steep. Conduction of thermal energyoccurs at a rate proportional to the temperature gradient in the exposedtissue. Lengthening the exposure time will reduce the maximumtemperature rise in exposed tissue.

[0047] For instance, at 1.3 microns the laser pulse width may be set to30 milliseconds and fluence to less than 30 joules per squarecentimeter. This prevents excessive heat build up in the epidermis,which is approximately the top 100 microns in skin. The papillary dermiscan then be heated to a therapeutic level without damage to theepidermis. The epidermis will reach a temperature higher than but closeto that of the papillary dermis.

[0048] The epidermis is more resilient in handling extremes oftemperature than most other tissue in the human body. It is thereforepossible to treat the papillary dermis in conjunction with the epidermiswithout scarring or blistering, by treating both layers with laserenergy and allowing a long enough exposure time such that the thermalgradient between the epidermis and underlying layers remains low. Inthis way the underlying layers can be treated without thermal damage tothe epidermis.

[0049] It is known that thermal damage in tissue is time dependant andbrief exposures to high temperature levels may be tolerated insituations where long exposures are lethal or injurious. Terminating theexposure of the epidermis to elevated temperatures will decrease therisk of damage to the epidermis. In this invention thermal quenching isused to terminate the exposure of the epidermis to elevatedtemperatures. In this embodiment cryogen spray cooling is use to reducethe epidermal temperature following the exposure to laser radiation. Thelaser heats the epidermis and lower layers simultaneously because ofpenetration of the laser energy into tissue. The cryogen cooling worksfrom the top surface and heat flows out of the lower layers byconduction over a time period equivalent to the thermal relaxation timeat each depth of tissue. As a result the epidermis is heated for ashorter time period than the papillary dermis or other deeper layers.

[0050] In this invention a top layer of tissue can be protected bylimiting the time of exposure to elevated temperatures, and deeperlayers are protected by the attenuation of light energy in tissue water.

[0051] The depth of protection due to cooling is determined by thedegree of cooling and the time delay after laser exposure. In theembodiment described here 30 milliseconds of cooling spray is appliedwithout delay, (within 5 milliseconds), after the termination of thelaser exposure. The cooling may be delayed to cause longer thermalexposures of the surface. The amount of cooling is enough to reduce thetemperature of the surface to non-therapeutic levels. Higher coolinglevels will terminate heat build up deeper in tissue.

[0052] A wavelength of 1.3 microns is used in this embodiment to treatthe middle layers of skin. Other wavelengths such as 1.45 or 2.1 micronsmay by used to treat more superficial layers of skin by this method. Itis important that the wavelength is chosen such that there is absorptionin tissue water such that the energy attenuation versus depth is fairlyuniform over an area of skin. The range of wavelengths longer than 1100nm in the infrared have this property. It is important that the energysource used for this invention is uniformly attenuated with depth intissue. Ultrasound, microwaves, and RF electrical current are examples.

[0053] Unless defined otherwise, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the present invention belongs. Although anymethods and materials similar or equivalent to those described can beused in the practice or testing of the present invention, the preferredmethods and materials are now described. All publications and patentdocuments referenced in the present invention are incorporated herein byreference.

[0054] While the principles of the invention have been made clear inillustrative embodiments, there will be immediately obvious to thoseskilled in the art many modifications of structure, arrangement,proportions, the elements, materials, and components used in thepractice of the invention, and otherwise, which are particularly adaptedto specific environments and operative requirements without departingfrom those principles. The appended claims are intended to cover andembrace any and all such modifications, with the limits only of the truepurview, spirit and scope of the invention.

[0055] The description that follows is presented to enable one skilledin the art to make and use the present invention, and is provided in thecontext of a particular application and its requirements. Variousmodifications to the disclosed embodiments will be apparent to thoseskilled in the art, and the general principals discussed below may beapplied to other embodiments and applications without departing from thescope and spirit of the invention. Therefore, the invention is notintended to be limited to the embodiments disclosed, but the inventionis to be given the largest possible scope which is consistent with theprincipals and features described herein.

[0056] In a preferred embodiment of the present invention, re-heating oftissue, especially target or subsurface tissue can be useful. U.S.application Ser. No. 09/185,490 filed Nov. 3, 1998 by Koop et al.teaches methods and systems for performing subsurface heating ofmaterial and in incorporated herein by reference in its entirety. Inthese methods, target or subsurface tissue is preheated to an elevated,non-destructive temperature which is somewhat below that of treatment.Thereafter, the temperature of the target tissue or structures is raisedto treatment temperature. Once this second increase in temperature isachieved, the target tissue or structures will conduct heat into thebody, especially to adjacent tissue and surface tissue, at which timethe post-cooling of the present invention can be initiated so as toprevent damage to adjacent tissue or dermis or other surface tissue.

[0057] Unless defined otherwise, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the present invention belongs. Although anymethods and materials similar or equivalent to those described can beused in the practice or testing of the present invention, the preferredmethods and materials are now described. All publications and patentdocuments referenced in the present invention are incorporated herein byreference.

[0058] While the principles of the invention have been made clear inillustrative embodiments, there will be immediately obvious to thoseskilled in the art many modifications of structure, arrangement,proportions, the elements, materials, and components used in thepractice of the invention, and otherwise, which are particularly adaptedto specific environments and operative requirements without departingfrom those principles. The appended claims are intended to cover andembrace any and all such modifications, with the limits only of the truepurview, spirit and scope of the invention.P

[0059] Thus, specific embodiments and applications of thermal quenchingof tissue have been disclosed. It should be apparent, however, to thoseskilled in the art that many more modifications besides those alreadydescribed are possible without departing from the inventive conceptsherein. The inventive subject matter, therefore, is not to be restrictedexcept in the spirit of the appended claims. Moreover, in interpretingboth the specification and the claims, all terms should be interpretedin the broadest possible manner consistent with the context. Inparticular, the terms “comprises” and “comprising” should be interpretedas referring to elements, components, or steps in a non-exclusivemanner, indicating that the referenced elements, components, or stepsmay be present, or utilized, or combined with other elements,components, or steps that are not expressly referenced.

What is claimed is:
 1. A device for treatment of skin, comprising: anenergy delivery system that directs energy to a target tissue for apredetermined time period and at a predetermined fluence such that apeak temperature reached in the target tissue causes a thermallymediated response resulting in transient erythema and/or mild edema,without blistering.
 2. The device of claim 1, fuirther comprisingcooling means for cooling a surface of the tissue after exposure to theenergy.
 3. The system of claim 1, wherein the energy is electromagneticenergy with a wavelength about 1.3 microns.
 4. The system of claim 1,wherein the cooling means delivers cryogenic fluids to the target tissueor structure together with tissues adjacent to the target tissue orstructure.
 5. The system of claim 1, wherein the predetermined fluenceon the skin surface is less than about 30 joules per square centimeterand the predetermined time period is greater than 10 milliseconds. 6.The system of claim 1, wherein the energy is ultrasound.
 7. The systemof claim 1, wherein the energy is electromagnetic radiation.
 8. Thesystem of claim 1, wherein the energy is provided by a laser.
 9. Thesystem of claim 1, wherein the energy is provided by at least one aflashlamp and a filament lamp.
 10. The system of claim 1, wherein theenergy comprises waves having a wavelength between a microwave and anultraviolet wave, inclusive.
 11. The system of claim 1, wherein thecooling means delivers a short spurt of cryogenic fluid subsequent todelivery of the energy.
 12. The system of claim 1, wherein the energyhas a pulse width between about 1 nanosecond and about 10 seconds. 13.The system of claim 1, wherein erythema and/or mild edema is achievedwithout the risk of high fluence levels or critical need for cooling.14. The system of claim 11, wherein the cooling means commences deliveryof the cryogenic fluid after the peak temperature is reached in thetarget tissue.
 15. The system of claim 11, wherein the cooling meansprovides cooling beginning after the heating of target tissue totreatment temperature.
 16. A method for treatment of skin, comprising:selecting a source of energy in which attenuation of the energy as itpasses through the skin is a function of depth; heating the skin withthe energy source for a predetermined time period and with apredetermined fluence such that the energy causes thermal mediatedinjury in skin below the epidermis resulting in transient erythema butdoes not blister the epidermis.
 17. The method of claim 16, using lightenergy having a wavelength at about 1.3 microns.
 18. The method of claim16, wherein the treatment is repeated serially with more than one daybetween any successive treatments.
 19. The method of claim 16, usinglight energy having a wavelength between 1100 nm and 270 nm.
 20. Themethod of claim 16, in which the selective thermally mediated treatmentof the target tissue or structures is for the treatment of vasculartissue.
 21. The method of claim 16, in which the selective thermallymediated treatment of the target tissue or structures is for thetreatment of tissue containing collagen.
 22. The method of claim 16, inwhich the selective thermally mediated treatment of the target tissue orstructures is for the treatment of cartilage.
 23. The method of claim16, in which the selective thermally mediated treatment of the targettissue or structures is for the treatment of tissue containing pigment.24. The method of claim 16, in which the selective thermally mediatedtreatment of the target tissue or structures is for the hair removaltreatment.
 25. A method for treatment of acne scars in skin, comprising:heating the target skin portion with a source of energy which isuniformly attenuated with depth in skin for a predetermined time periodand predetermined fluence such that the exposure time of the epidermisand the peak temperature reached by the epidermis are such that theepidermnis does not blister; and causing thermally mediated injury inskin below the epidermis resulting in transient erythema to initiate ahealing response which improves the appearance of the acne scars.
 26. Amethod for treatment of photo damaged skin, comprising: heating the skinwith a source of energy which is uniformly attenuated with depth in skinfor a predetermined time period and predetermined fluence such that theexposure time of the epidermis and the peak temperature reached by theepidermis are such that the epidermis does not blister; and causingthermal mediated injury in skin below the epidermis resulting intransient erythema to initiate a healing response which improves theappearance of the photo damaged skin.
 27. A method for treatment ofwrinkled skin, comprising: heating the skin with a source of energywhich is uniformly attenuated with depth in skin for a predeterminedtime period and predetermined fluence such that the exposure time of theepidermis and the peak temperature reached by the epidermis are suchthat the epidermis does not blister; and causing thermal mediated injuryin skin below the epidermis resulting in transient erythema to initiatea healing response which improves the appearance of the wrinkled skin.28. A method of thermal quenching of surface tissue during selectivethermally mediated treatment of target tissue or structures, the methodcomprising the steps of: delivering energy to the target tissue orstructures to increase the temperature of the target tissue orstructures to a predetermined treatment temperature, thereby, resultingin transient erythema; and cooling the surface tissue or other tissueadjacent the target tissue or structures to prevent excessive heating ofthe surface tissue or other tissue adjacent the target tissue.
 29. Themethod of claim 28 in which the step of cooling is initiated afterelevation of the target tissue or structures to treatment temperature.30. The method of claim 28 in which the step of cooling is initiatedprior to elevation of the target tissue or structures to treatmenttemperature.
 31. The method of claim 28 in which the step of cooling isinitiated concurrently with elevation of the target tissue or structuresto treatment temperature.
 32. The method of claim 28 in which the stepof cooling is initiated subsequent to an increase in the temperature ofthe surface tissue or other tissue adjacent the target tissue orstructures.
 33. The method of claim 28 in which the pulsedelectromagnetic energy is delivered at a rate of between about 50 Joulesper square centimeter and about 150 Joules per square centimeter. 34.The method of claim 28 in which the pulsed electromagnetic energy has apulse width of between about 5 milliseconds and about 200 milliseconds.35. The method of claim 28 in which the step of cooling includesdelivery of refrigerant to the surface tissue for a period of betweenabout 10 milliseconds and about 30 milliseconds.
 36. The method of claim28 in which the step of cooling the surface tissue or other tissueadjacent the target tissue or structures is performned using passivecooling means.
 37. The method of claim 28 in which the step of coolingthe surface tissue or other tissue adjacent the target tissue orstructures is performed using dynamic cooling means.
 38. The method ofclaim 28 wherein the target tissue or structures is veins and in whichthe treatment is vascular treatment.
 39. The method of claim 28 whereinthe target tissue or structures is hair follicles and wherein thetreatment is hair removal.
 40. The method of claim 37 wherein thedynamic cooling means cools the surface tissue or other tissue adjacentthe target tissue or structures by delivering a liquid refnigerant tothe surface tissue or other adjacent the target tissue or structures.41. The method of claim 28 wherein the target tissue or structures istissue containing pigmentation and in which the treatment ismodification of the pigmentation.
 42. The method of claim 37 in whichthe dynamic cooling means cools the surface tissue or other tissueadjacent the target tissue or structures by delivering a liquidrefrigerant to the surface tissue or other tissue adjacent the targettissue or structures.
 43. The method of claim 42 in which the liquidrefrigerant is delivered to the surface tissue or other tissue adjacentthe target tissue or structures for a period of time between about 10milliseconds and about 30 milliseconds.